lib/Kconfig.debug: Allow BTF + DWARF5 with pahole 1.21+

Commit 98cd6f52 ("Kconfig: allow explicit opt in to DWARF v5")
prevented CONFIG_DEBUG_INFO_DWARF5 from being selected when
CONFIG_DEBUG_INFO_BTF is enabled because pahole had issues with clang's
DWARF5 info. This was resolved by [1], which is in pahole v1.21.

Allow DEBUG_INFO_DWARF5 to be selected with DEBUG_INFO_BTF when using
pahole v1.21 or newer.

[1]: https://git.kernel.org/pub/scm/devel/pahole/pahole.git/commit/?id=7d8e829f636f47aba2e1b6eda57e74d8e31f733cSigned-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220201205624.652313-6-nathan@kernel.org

lib/Kconfig.debug

@@ -296,7 +296,7 @@ config DEBUG_INFO_DWARF4
 config DEBUG_INFO_DWARF5
 	bool "Generate DWARF Version 5 debuginfo"
 	depends on !CC_IS_CLANG || (CC_IS_CLANG && (AS_IS_LLVM || (AS_IS_GNU && AS_VERSION >= 23502)))
-	depends on !DEBUG_INFO_BTF
+	depends on !DEBUG_INFO_BTF || PAHOLE_VERSION >= 121
 	help
 	  Generate DWARF v5 debug info. Requires binutils 2.35.2, gcc 5.0+ (gcc
 	  5.0+ accepts the -gdwarf-5 flag but only had partial support for some